1. Field of the Invention
The present invention relates to a display apparatus in which pixels including light emitting devices are arranged in a matrix. More particularly, the present invention relates to a so-called active-matrix display apparatus in which the amount of a current flowing through a light emitting device, such as an organic EL device, etc., is controlled by an insulated-gate field effect transistor disposed in each pixel. Also, the present invention relates to a method of driving such a display apparatus, and an electronic system including such a display apparatus.
2. Description of the Related Art
In an image display apparatus, such as a liquid crystal display, for example, an image is displayed by arranging a large number of liquid crystal pixels in a matrix and controlling the transmission intensity or the reflection intensity of incident light for each pixel in accordance with image information to be displayed. This is the same for an organic EL display, etc., using an organic EL device as a pixel. However, the organic EL device is a self-emitting device unlike a liquid crystal pixel. Thus, the organic EL display has advantages of having high visibility of an image, unnecessary of back lighting, and high response speed compared with a liquid crystal display. Also, the luminance level (grayscale) of each light emitting device can be controlled by the amount of current flowing therethrough. The organic EL display is greatly different from a voltage-controlled type display, such as a liquid crystal display, in the point of being a so-called current-controlled type.
In the same manner as a liquid crystal display, for a driving method of an organic EL display, there are a simple matrix method and an active matrix method. The former has a simple structure, but has problems, such as it is difficult to achieve a large-scale and high-definition display.
Accordingly, active-matrix displays are currently being developed widely. In this method, a current flowing through a light emitting device in each pixel circuit is controlled by an active device (in general, a thin-film transistor: TFT) disposed in the pixel circuit. The descriptions thereof are disclosed in Japanese Unexamined Patent Application Publication Nos. 2003-255856, 2003-271095, 2004-133240, 2004-029791, 2004-093682, and 2006-215213.